There are numerous types of Uninterruptible Power Supply (UPS) systems for supplying backup alternating current (AC) or direct current (DC) power to electrical loads. These UPS systems generally use batteries or types of other energy storage devices that supply such power when a main power supply (e.g., line power) is not available. For example, backup power is provided when power from an AC source performs outside acceptable limits or fails altogether.
These UPS systems generally use multiple energy storage devices configured in parallel or in series to provide backup power. In such systems, it is important to be able to accurately estimate the remaining time period that the UPS system can supply backup power. Conventionally, UPS systems connected to energy storage devices estimate the time remaining by modeling each of the many devices in the system, and performing a calculation that estimates the time remaining. For instance, the UPS system generally models devices such as batteries based on what types of batteries are installed in the UPS system. The different types of batteries are identified using a number of methods. One way of identifying battery types includes manually (e.g., by a system administrator) identifying each battery type, and program the battery type into the time remaining calculation using an interface of the UPS.
In another instance, a resistor is included within each battery, the resistor having a resistance value that is correlated with a particular type of battery. The UPS is configured to measure the resistance of the resistor in the battery and therefore identify the type of battery installed within the UPS system. However, with each new type of battery type provided, a new resistor value is required to uniquely identify the new type of battery, and therefore the UPS system needs to recognize the new resistance and battery type. Because of this method, a very limited number of different battery types can be supported by a particular UPS. What is needed is a more flexible and accurate way of recognizing and modeling batteries to estimate time remaining in a UPS system.
Also, because batteries fail from time to time, either from overuse (e.g., charging and discharging cycles) or being exposed to other conditions (e.g., an over-temperature condition) that cause the batteries to be incapable of storing energy, it is beneficial to monitor batteries by the UPS system to identify failed batteries that might affect the performance of the UPS system. Several conventional systems monitor such parameters as battery temperature, float voltage, etc. for each battery, and provide alarms indicating that a particular battery has failed. In such systems, such monitoring is provided by either a monitoring subsystem installed in each battery or a monitor of the UPS allocated to each battery module.